1. Field of the Invention
The present invention relates to liquid ejection heads ejecting liquids, methods for manufacturing the liquid ejection heads, and methods for forming structures. The present invention particularly relates to a liquid ejection head that ejects ink toward a recording medium to perform recording, a method for manufacturing the liquid ejection head, and a method for forming a microstructure useful in semiconductor manufacture.
2. Description of the Related Art
An example of a process using a liquid ejection head ejecting a liquid is an ink jet recording process (liquid-ejecting recording process).
In general, ink jet recording heads used for the ink jet recording process include fine discharge ports, liquid passages, and energy-generating elements which are disposed in the liquid passages and which generate energy used to eject a liquid. A method for manufacturing such an ink jet recording head is disclosed in, for example, U.S. Pat. No. 5,478,606.
A pattern for forming passages is formed on a substrate having energy-generating elements using a soluble resin; a covering resin layer, containing an epoxy resin and a cationic photopolymerization initiator, for forming walls of the passage is formed on the pattern; discharge ports are formed on the energy-generating elements by photolithography; the soluble resin is dissolved off; and the covering resin layer is finally cured, whereby the passage walls are formed.
The method disclosed in U.S. Pat. No. 5,478,606 has a certain limitation in patterning accuracy because of a material currently used and is, however, capable of forming passage walls 101 well at a nozzle density of up to 600 dpi as shown in FIG. 7. With reference to FIG. 7, reference numeral 103 represents energy-generating elements which are arranged on a substrate and which generate energy used to eject a liquid. The passage walls 101 have an aspect ratio (height-to-length ratio) of 4:3. There is a problem in that it is difficult to form the passage walls 101 well at a nozzle density of 1,200 dpi because the resolution of a mold member containing a photosensitive material is insufficient. For example, when the passage walls 101 are spaced from a nozzle adhesion-improving layer 102 as shown in FIG. 8, nozzles adjacent to each other are communicatively connected to each other and therefore are affected by crosstalk. This may affect the ejection of ink.
A possible measure against the problem is to replace the photosensitive material with a high-resolution material. However, it is difficult to immediately develop such a high-resolution material. Another possible measure against the problem is to reduce the thickness of the mold member. An increase in nozzle density to 1,200 dpi leads to a reduction in the length of each passage. This may causes the nozzles to be insufficiently refilled with ink. In order to keep the cross-sectional area of the passage and in order to prevent the insufficient refilling thereof, the height of the passage needs to be high. A reduction in the thickness of the mold member, which is used to form the passage, leads to a reduction in the height of the passage and therefore is practically difficult. The above two measures may be impractical in solving the problem due to an increase in nozzle density.